There are a large number of conventional techniques in which a wireless communication technique is applied to a surveillance camera system (for example, Patent Literature 1 and Patent Literature 2). For example, systems for transmitting a video taken by a surveillance camera through a wireless LAN (Local Area Network) are disclosed in Patent Literature 1 and 2. Furthermore, a system with a QoS (Quality of Service) function in a wireless LAN system using extended MAC (Media Access Control) of IEEE 802.11e is disclosed in Patent Literature 3.
Conventionally, two functions, DCF (Distributed Coordination Access) and PCF (Point Coordination Channel Access) are defined in the MAC of IEEE 802.11 standard. Furthermore, EDCA (Enhanced Distributed Channel Access) with QoS characteristics obtained by extending the DCF and HCCA (Hybrid coordinated function Controlled Channel Access) obtained by extending the PCF are defined in extended MAC of IEEE 802.11e.
The DCF and the EDCA are systems based on CSMA (Carrier Sense Multiple Access), and contention-based access means is provided to a terminal. The PCF and the HCCA are access methods using a polling system, and contention-free access means is provided to a terminal. A reference scheduling method using the HCCA is also disclosed in the IEEE 802.11e standard.